To build up composite thermal insulation systems (CTIS), insulation boards, for example rigid foam boards or rock wool slabs, are usually fastened by means of an adhesive mortar to the masonry, a reinforcing layer into which woven reinforcing fabrics, usually woven fiberglass fabrics, are laid is subsequently applied to the insulation boards and the composite system is finally covered with a surface render. Thus, DE-A 2516916 or DE-A 4216204 describes the production of reinforcing layers by firstly applying polymer-modified building compositions containing from 8 to 17% by weight of hydraulically setting binders to insulation boards and subsequently embedding woven fiber fabrics, for example woven fiberglass fabrics or fiberglass meshes. Coatings which are free of woven reinforcing fabrics are not described. In DE-A 4216204, it is recommended that buildings be thermally insulated by providing them with mineral insulation boards and a cement-based layer of render containing from 15 to 28% by weight of hydraulically setting binders, with a woven fiber fabric being embedded between the thermal insulation boards and the layer of render. The layer of render can additionally contain fiber materials or polymers as adhesion promoters.
Thus, the application of woven fiber fabric-reinforced reinforcing layers to thermal insulation boards in principle requires a plurality of operations. In one step, the reinforcing composition is applied to the thermal insulation board, the woven reinforcing fabric is embedded in the reinforcing composition in a further step and the reinforcing composition is finally smoothed. The introduction of the woven reinforcing fabric into the applied reinforcing composition represents a step which not only costs working time but also material (woven reinforcing fabric). It would be simpler to process and less labor-intensive if a reinforcing layer which is free of woven reinforcing fabric were to have the same properties after curing as a conventional reinforcing layer consisting of reinforcing composition and additionally incorporated woven reinforcing fabric.
Some approaches to producing composite thermal insulation systems which are free of woven reinforcing fabric are already known. Thus, DE-A 10248098 describes composite thermal insulation systems comprising insulation boards and a fiberglass-reinforced, cement-based layer of render. DE-A 2622465 describes fiber-containing cement-based renders. The fiber-containing renders of DE-A 10248098 and of DE-A 2622465 are not modified with polymers based on ethylenically unsaturated monomers. The renders of DE-A 19624149, too, do not contain any polymers based on ethylenically unsaturated monomers. In DE-A 3429251, synthetic resin coating compositions containing crosslinked or crosslinkable polymers having glass transition temperatures Tg below −15° C. and optionally additional fibers are used for coating thermal insulation layers. The use of precrosslinked or crosslinkable polymers leads to brittle renders with the risk of crack formation. In DE-A 102004048584, exterior render preparations comprising carbon fibers and binders are recommended for producing composite thermal insulation systems reinforced with woven fiber fabrics. DE-A 19839295 relates to composite thermal insulation systems composed of lightweight mineral insulation boards which have been coated with a hydraulic lightweight render and are adhesively bonded to the lightweight render along the joints. The hydraulic lightweight render contains from 10 to 30% by weight, based on the dry composition, of hydraulically setting binders, polymer dispersions and cotton fibers. DE-A 4032769 recommends coating compositions comprising binders based on polymer dispersions or inorganic binders for composite thermal insulation systems. DE-A 3040077 discloses a rendering dry mortar for coating insulation boards, with the rendering dry mortar containing glass fibers, polymeric binders and at least 10% by weight, based on the dry composition, of hydraulically setting binders. DE-A 2703342 describes mortars containing polymers, fibers and from 15 to 40% by weight, based on the dry composition, of hydraulically setting binders for coating thermal insulation boards. DE-A 19950441 describes fiber-modified wall renders which contain copolymers based on acrylic esters and styrene and also ethylhydroxyethylcellulose as binders. DE-A 102008043988 recommends fiber-containing, polymer-modified dry mortar formulations which additionally contain from 10 to 30% by weight of hydraulically setting binders for producing composite thermal insulation systems.
Furthermore, DE-A 19624149 describes fiber-modified renders for décor purposes. DE-A 19903756 recommends décor renders containing organic polymers as binders and also fillers and polymer flocks as further components.
Despite the many approaches to the production of fiber-containing reinforcing layers, there is a need for building compositions in which the fibers are more compatible and interact more strongly with the further components of the reinforcing layers and, associated therewith, lead to composite thermal insulation systems having improved mechanical properties and a lower tendency for cracks to be formed.
In the light of this background, it was an object of the invention to provide fiber-containing paste-like building compositions with which the abovementioned disadvantages can be overcome.